80 DESCRIPTION OP NEW 



dulated at the tip; ligament rather long and thin; epidermis very dark-brown, somewhat 

 wrinkled, and scarcely showing the lines of growth; cardinal teeth compressed, single in 

 the right and double in the left valve, elevated, slightly crenulate, the anterior being the 

 most elevated ; lateral teeth long and somewhat curved; anterior cicatrix distinct; pos- 

 terior cicatrix confluent; dorsal cicatrices placed in the centre of the cavity of the beaks; 

 cavity of the shell rather shallow; cavity of the beaks shallow and angular; nacre white 

 and iridescent. 



Remarks. — Five female and three male adults, with two young shells of this species 

 were received from Dr. Hale, at different times. The females are a good deal enlarged 

 over the posterior slope, and spread out on the posterior basal margin. It seems to be 

 nearly allied to Nashvi/lianus, Nobis, and to Hakianus, Nobis. It is not so large or 

 pearly a nacre as the latter, nor does it seem to grow quite so large as the former. In 

 the beaks it also differs from it. In some of the old specimens indistinct rays may be 

 observed through the very dark surface. In the two young shells rays may be observed 

 on the whole disk. The undulations of the beaks are small and very closely set. 



Unio spatulatus. PI. VIII. Fig. 22. 



Testa Isevi, ellipticd, compressd ; valvulis subtenuibus; natibus vix prominvlis, ad apicem andulatis; epider- 

 •mide luted, valde radiata; denlibus cardinalibus parvis ; lateralibus longis rectisque; margarita alba et iri- 

 descenle. 



Shell smooth, elliptical, compressed; valves rather thin; beaks slightly prominent and undulated at the beak; 

 epidermis yellowish, with numerous rays; cardinal teeth small; lateral teeth long and straight; nacre white and 

 iridescent. 



Ilab. Rock River, Wisconsin. Captain Maryatt and B. W. Budd, M. D. 



My cabinet and cabinet of Dr. Budd. 

 Diam. .6, Length .9, Breadth 1.5 inches. 



Shell smooth, elliptical, compressed, very inequilateral; substance of the shell rather 

 thin; beaks but slightly prominent and minutely undulate at the tips; ligament long and 

 thin; epidermis yellowish, with numerous green rays nearly over the whole disk; cardinal 

 teeth very small and pointed, double in the left and single in the right valve ; lateral teeth 

 long and straight; anterior cicatrices distinct; posterior cicatrices confluent; dorsal cica- 

 trices placed in the centre of the cavity of the beaks; cavity of the shell shallow; cavity 

 of the beaks shallow and angular; nacre white. 



Remarks. — Many years since Captain Maryatt sent me a box of shells from Wisconsin, 

 in which there was a single imperfect specimen of this species. Although pretty well 

 convinced that it was new and undescribed, I delayed inserting it in my former paper, in 

 the hope of getting better specimens. Dr. Budd has submitted to my examination two 

 perfect specimens, neither being eroded even on the beaks, which are finely undulated. 

 It has some resemblance to IT. iris, Nobis, but is a shorter and a more ponderous shell. 

 It also bears some resemblance to the young of IT. crassus, Say, and to IT ellipsiformis, 

 Conrad, but differs from the latter in the form of the cardinal tooth, and in the beaks, 

 which Mr. Conrad describes as simple, while in the spatulatus they are undulate. 



